A well-known problem for vehicles such as robots, wheelchairs, hand trucks, and the like, is to provide some mechanism to overcome obstacles, such as stairs, curbs, and the like, that will be in the path of the vehicle.
United States Application Patent Number 2011/0127732 of Mann et al. provides a wheel with a circular perimeter for smooth rolling on travel surface, and movable protrusions that are withdrawn into the wheel for regular travel, and that can be extended radially outward from the perimeter to engage and climb stairs.
U.S. Pat. No. 4,421,189 to Watkins et al. provides a spoked wheel with a small wheel rotatably mounted on the outer end of each spoke. On a level surface the spoked wheel is stationary, and the vehicle rolls on the small wheels. When a stair is encountered, the spoked wheel turns and the small wheels engage the top of each step in turn as the spokes turn, pulling the wheel and vehicle up the stairs.
U.S. Pat. No. 7,363,994 to DeFazio provides a plurality of wheels on each side of a wheeled platform where the perimeter of the wheels overlap. Small spokes extend from the perimeter of each wheel and engage stairs to climb same.
U.S. Pat. No. 4,919,489 to Kopsco discloses a wheel having an elastomeric flexible outer annulus upon which the wheel normally rides. Parallel spaced sprockets receive the annulus and include individual cogs which extend less radially outwardly than the annulus. When an obstacle is encountered, the flexible annulus yields, thereby enabling a protruding cog to engage the obstacle and pivot around it thereby lifting the vehicle over the obstacle.
U.S. Pat. No. 6,422,576 to Michaeli and U.S. Pat. No. 3,179,431 to Pikl similarly disclose wheels where the outer perimeter flexes radially inward when encountering a stair edge, thereby forming a protrusion to engage the step and move the wheel upward.
Amphibious vehicles require a propulsion mechanism operative both on land and water. U.S. Pat. No. 7,942,710 to Gaither discloses an amphibious all-terrain vehicle that has separate hydraulic wheel and propeller drives, however it is also well known to use only a wheel drive. The wheels themselves can have treads or pockets on the outer perimeter to engage the water for propulsion, for example as disclosed in U.S. Pat. No. 7,445,530 to Munshaur et al., U.S. Pat. No. 4,664,051 to Newkirk, and U.S. Pat. No. 5,058,643 to Nakasaki. U.S. Pat. No. 3,688,731 to Houle discloses a system where an impeller wheel is mounted on a driven axle and is configured to be above the ground when on land, and to engage the water when the vehicle is floating.